Florida Scrub - United States Fish and Wildlife Service

[Pages:38]Florida Scrub

Including Scrubby Flatwoods and Scrubby High Pine

FNAI Global Rank: FNAI State Rank: Federally Listed Species in S. FL: State Listed Species in S. FL:

G2/G3 S2 32 100

Florida scrub. Original photograph courtesy of The Nature Conservancy.

Florida scrub is a plant community easily recognized by the dominance of evergreen shrubs and frequent patches of bare, white sand. With more than two dozen threatened and endangered species dependent upon scrub, the entire community is itself endangered. Recovery of the community and its associated plants and animals will depend upon land acquisition and effective land management.

Synonymy

Florida scrub in its various phases has been called xeric scrub, sand scrub, big scrub, sand pine scrub, oak scrub, evergreen oak scrub, dune oak scrub, evergreen scrub forest, slash pine scrub, palmetto scrub, rosemary scrub, and rosemary bald. Florida scrubs may be classified as coastal or interior. Scrubs are often named by the dominant plant species, as in rosemary scrub, sand pine scrub, palmetto scrub, or oak scrub. Some authors have confused closed-canopy forests of sand pine trees with scrub. Scrubs that are very recent in origin, usually a result of mans activities, are called pioneer scrubs. Communities intermediate between scrub and pine flatwoods have been called dry or xeric flatwoods but now are referred to as scrubby flatwoods. Communities intermediate between scrub and high pine have been called southern ridge sandhills, hickory scrub, yellow sand scrub, turkey oak scrub, turkey oak barrens, and natural turkey oak barrens, but probably are best referred to as scrubby high pine. The FLUCCS code for the scrub community include: 413 (sand pine), 421 (xeric oak), and 441 (coniferous plantations).

Distribution

Coastal Florida scrub occurs sporadically on barrier islands and dunes and ridges along the Atlantic Coast in Florida and Georgia and along the Gulf Coast in Florida and Alabama (Myers 1990, Wharton 1978). On the northern Gulf Coast, coastal scrubs occur on several barrier islands

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and on a narrow band along the coast from Franklin County to just across the state line in Baldwin County, Alabama. There are only a handful of coastal scrubs on the Gulf coast of the Florida peninsula. Among these are scrubs in the vicinity of Cedar Keys in Levy County, near WeekiWatchee in Hernando County, near Palma Sola in Manatee County, and near Bonita Springs, Naples and Marco Island in Lee and Collier counties. On the Atlantic coast of the Florida peninsula, scrubs occur (or formerly occurred) from St. Johns County south to Miami-Dade County, where they occupy dunes and ridges immediately inland from coastal strand.

Within the South Florida Ecosystem, coastal scrubs occur in Indian River, St. Lucie, Martin, Palm Beach, and Broward counties on the Atlantic Coast, and Lee and Collier counties on the Gulf Coast. Coastal scrub formerly occurred in Miami-Dade County.

Interior Florida scrub occur sporadically on well-drained sandy ridges on the Georgia Fall Line and within the Florida peninsula from Kingsley Lake, Clay County south to Immokalee, Collier County (Myers 1990, Wharton 1978). Most interior Florida scrubs are associated with north-south tending ridges that were formed by wind and wave action during periods of higher sea level. The expansive stands of sand pine in the Ocala NF in Lake and Marion Counties are forests, not scrub, and occupy a landscape with yellow sand that may have supported high pine savanna during the earlier Holocene.

Within the South Florida Ecosystem, interior Florida scrub occurs on the Lake Wales, Winter Haven, Lake Henry, Lakeland, and Bombing Range ridges (White 1970) in Polk, Osceola, and Highlands counties; on lesser ridges within the Osceola Plain and Eastern Valley in Osceola, Okeechobee, Indian River, St. Lucie, and Martin counties; and scattered on small rises in Hardee, DeSoto, Glades, Hendry, and Collier counties (Figure 1).

Scrubby flatwoods is a scrub-like association often occurring on drier ridges in typical flatwoods or near coasts. The understory species of this vegetation type are similar to those of sand pine scrub, but the sand pine is replaced by slash pine or longleaf pine. Scrubby flatwoods occur throughout Florida, including the panhandle and northern peninsula where scrub is rare or nonexistent. Scrubby flatwoods occupy slightly higher and better-drained areas than pine flatwoods. Scrubby flatwoods are common on the Archbold Biological Station and formerly occupied much of the western flank of the Lake Wales Ridge. This community is especially well-developed on the low north-south tending ridges in Osceola and Okeechobee counties.

Scrubby high pine occurs throughout Florida where it usually is associated with peaks in high pine communities or narrow bands along steep slopes between high pine and wetlands. It sometimes occurs on well-drained sandy peaks within pine flatwoods communities. In northern Florida and the panhandle, the community generally occurs in small isolated patches. Within the South Florida Ecosystem, however, scrubby high pine once dominated much of the southern Lake Wales Ridge, especially in four regions on the eastern flank including areas around Catfish Creek, Tiger Creek, Carter Lake and (formerly) Bear Hollow (Christman 1988a). High pine and scrubby high pine (called southern ridge sandhills by Abrahamson et al. 1984, and others) apparently were the native plant communities of choice for citrus growers on the Lake Wales Ridge.

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Multi-Species Recovery Plan for South Florida

Figure 1. Conservation lands and topography in South Florida north of Lake Okeechobee.

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Description

There is no single plant species that occurs in all Florida scrubs and not in other habitats as well, yet the community is easily recognized. Florida scrub can be identified by the dominance of several species of woody shrubs, especially myrtle oak or scrub oak (Quercus myrtifolia or Q. inopina), sand live oak (Q. geminata), Chapmans oak (Q. chapmanii), crookedwood (Lyonia ferruginea), saw palmetto (Serenoa repens) and Florida rosemary (Ceratiola ericoides); the absence of a tree canopy; the absence of a continuous vegetative ground cover; and the absence of longleaf pine (Pinus palustris), wiregrass (Aristida beyrichiana), and turkey oak (Q. laevis). When sand pines (Pinus clausa) are present in scrub they do not form a continuous canopy but occur as scattered individuals or clumps of individuals. Most scrubs occur on white sand and patches of bare sand with or without scattered clumps of ground lichens.

Scrub soils are derived from quartz, slightly to strongly acidic, very low in nutrients, and moderately to excessively well-drained. They are classified as entisols (soils with little or no horizon development) (Myers 1990). Scrub soils are practically devoid of organic matter, silt and clay. Scrub soils range from the pure white, excessively leached St. Lucie Fine Sand, to moderately leached Paola and Orsino sands that are characterized by a white surface and a yellowish subsoil.

Scrubs often occupy ecotones between longleaf pine savannas (high pine or pine flatwoods) and wetlands, and conditions within a single scrub may grade from xeric to mesic. Scrubs on the most excessively drained sites often are dominated by Florida rosemary and referred to as rosemary balds. Sand pine scrubs have scattered individuals or clumps of sand pines and oak scrubs are dominated by one or more of the shrubby oaks.

Scrubby flatwoods is floristically and functionally intermediate between pine flatwoods and scrub, and sometimes (but not necessarily) occurs as an ecotone between them (Abrahamson and Hartnett 1990). Scrubby flatwoods differs from scrub by the presence of scattered wiregrass and a preponderance of flatwoods species such as fetterbush (Lyonia lucida), wax myrtle (Myrica cerifera), and gallberry (Ilex glabra). Shrubby oaks, including sand live oak, Chapmans oak, and myrtle oak or scrub oak, are often dominant and slash pine, sand pine or longleaf pine may be present. Plant species typical of scrubby flatwoods that may be considered indicators of the community include tarflower (Befaria racemosa), scrub St. Johns wort (Hypericum reductum), and pennyroyal (Piloblephis rigida). Scrubby flatwoods is more mesic than scrub, has a higher water table (Abrahamson et al. 1984) and the vegetation is more dense. Scrubby flatwoods is drier that flatwoods and almost never has standing water (Abrahamson et al. (1984). It has been suggested that scrubby flatwoods sometimes captures pine flatwoods sites that have been logged and protected from fire (see Myers 1990).

Scrubby high pine, called southern ridge sandhills by Abrahamson et al. (1984), yellow sand scrub by Christman (1988a), natural turkey oak barrens by Christman and Judd (1990), hickory scrub by Main and Menges (1997), Caribbean pine-turkey oak by Laessle (1967), slash pine-turkey oak by Douglas and Layne (1978), and blackjack lands or blackjack ridges by 19th century land surveyors cited in Myers (1990) is a rare, naturally

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Multi-Species Recovery Plan for South Florida

occurring plant community that is floristically and functionally intermediate between scrub and high pine. Scrubby high pine contains longleaf pine or south Florida slash pine (Pinus elliottii var. densa), turkey oak and scattered wiregrass, and has yellow sand, conditions typical of high pine. However scrubby high pine also contains typical scrub species, such as sand pine, evergreen scrub oaks, garberia (Garberia fruticosa), and rosemary, and it supports several species that are nearly restricted to it or reach their greatest abundances in it such as scrub hickory (Carya floridana), scrub beargrass (Nolina brittoniana), pigeonwing (Clitoria fragrans), Lewtons polygala (Polygala lewtonii), and the scrub balms (Dicerandra spp.) (Christman 1988a, 1988b; Christman and Judd 1990). Scrubby high pine easily is confused with man-made turkey oak barrens but references from the 18th and 19th centuries (cited in Myers 1990) attest to the natural occurrence of scrubby high pine long before the original longleaf pine savannas were logged. Scrubby high pine appears to be associated with topographically diverse landscapes where longterm fire-return intervals have been exceedingly variable (Myers and Boettcher 1987, Christman 1988b, Myers 1990).

Narrow bands of scrubby high pine often occur as ecotones on steep slopes between high pine and wetland communities. (Note that on more gentle slopes high pine usually grades almost imperceptibly into pine flatwoods.) Scrubby high pine also occurs on ridges or peaks within high pine communities perhaps because the soils there are too well-drained to support a continuous ground cover of the wiregrass needed to carry frequent fires. The community also occurs on rolling hills interspersed with ponds and marshes, especially on the Lake Wales Ridge (Christman 1988a). Scrubby high pine apparently was always uncommon in central and northern Florida, but formerly was common on the southern Lake Wales Ridge where, prior to its almost complete conversion to citrus orchards, it occupied sites with extremely well-drained sands and extremely varied topography (Christman and Judd 1990, Myers 1990).

Species Diversity

Table 1 lists the vertebrates that are characteristic of Florida scrub. All are endemic to the State of Florida. Other xeric-adapted species that are almost always encountered in scrub include the Florida mouse (Podomys floridana), the short-tailed snake (Stilosoma extenuatum), the scrub lizard (Sceloporus woodi), the rufous-sided towhee (Pipilo erythrophthalmus), the gopher tortoise (Gopherus polyphemus), the Florida worm lizard (Rhineura floridana), other subspecies of mole skinks (Eumeces egregius sspp.), and the crowned snakes (Tantilla relicta spp.). Although these animals are typically encountered in scrub, none are entirely restricted to the community; rather they are animals adapted to xeric habitats in general (Campbell and Christman 1982).

There are also many species of invertebrates that are endemic to Florida scrub. Deyrup (1989) listed 46 species of insects and spiders believed to be restricted to scrub, including 20 species restricted to scrub within the South Florida Ecosystem.

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Table 2 provides a list of characteristic and occasional plant species known to occur in interior scrub, coastal scrub, scrubby flatwoods, and scrubby high pine. Many of these are listed as endangered or threatened by the FWS and are treated in The Species section of this recovery plan. Among the scrub endemic plants that are not federally listed are the scrub milkweed (Asclepias curtissii), Florida rosemary (Ceratiola ericoides), garberia (Garberia heterophylla), scrub rockrose (Helianthemum nashii), scrub holly (Ilex cumulicola), nodding pinweed (Lechea cernua), scrub hickory (Carya floridana), scrub palm (Sabal etonia), and sand pine (Pinus clausa), all of which are fairly widespread in Florida scrub. Some of these, such as sand pine, Florida rosemary, and garberia often invade disturbed high pine sites (turkey oak barrens) and probably are not in need of protection. Others, such as scrub milkweed, nodding pinweed, scrub palm and scrub rockrose may be more restricted to scrub and scrubby flatwoods and therefore in greater danger of extinction.

Wildlife Species of Concern

Federally listed animal species that depend upon or utilize Florida scrub, scrubby flatwoods, or scrubby high pine in South Florida include: the Florida panther (Puma (=Felis) concolor coryi), Florida scrub-jay (Aphelocoma coerulescens), Kirtlands warbler (Dendroica kirtlandii), eastern indigo snake (Drymarchon corais couperi), blue-tailed mole skink (Eumeces egregius lividus), and sand skink (Neoseps reynoldsi). Biological accounts and recovery tasks for these species are included in The Species section of this recovery plan. These species are also included in Appendix C.

The Florida mouse (Podomys floridanus) is the only species of mammal entirely restricted to Florida. Florida mice occur in open scrub, scrubby flatwoods, scrubby high pine and high pine communities where they live in burrows, especially those of the gopher tortoise. Characteristics of the habitat that favor Florida mice are similar to those that favor the Florida scrub-jay (Layne 1992). The Florida mouse is larger than other deer mice and its closest relatives apparently are in southern Mexico (Layne 1992). The Florida mouse is listed as a species of special concern by the State of Florida because of habitat loss throughout its limited range in the central peninsula.

The sand skink (Neoseps reynoldsi) is listed as a threatened species by the State and the FWS. This species is restricted to the microhabitats of loose sand and sunny exposures primarily in the rosemary scrub habitat of central Florida. In addition, it can be found inhabiting sand pine scrub, oak scrub, scrubby flatwoods, turkey oak barrens (Moler 1992), and was reported from definite high pine (sand hills) sites by Telford (1962) in ecotonal areas between high pine and sand pine forest in the Ocala NF. Because sand skinks spend most of their time 1 to 8 cm (0.5-3.0 in) beneath the surface of well-drained sandy soils, they cannot tolerate dense ground cover or heavily rooted vegetation. This habitat has already seen much destruction as a result of agriculture and residential development. Although the sand skink is threatened due to loss of

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Florida mouse. Original photograph by Barry Mansell.

Multi-Species Recovery Plan for South Florida

habitat, it is often found in the remnant habitat that exists. Since the specialized habitat of the sand skink is rapidly declining, conservation actions should be taken to preserve large tracts of scrub and high pine communities.

The gopher tortoise (Gopherus polyphemus) is a state listed species that occurs in scrub, as well as other upland communities (Appendix C). Its deep burrows provide sites for nesting, feeding, refuge from fire and predators, and protection from high temperatures and desiccation for hundreds of other species (Landers and Speake 1980, Diemer 1992, Enge et al. 1997). Gopher frogs (Rana capito), Florida mice (Podomys floridana), and eastern indigo snakes (Drymarchon corais couperi) are variously dependent on tortoise burrows. The spoil in front of a gopher tortoise burrow provides germination sites for plants and essential microhabitat for fossorial reptiles such as mole skinks (Eumeces egregius), and crowned snakes (Tantilla relicta). Over 300 species of invertebrates, 36 reptiles and amphibians, 19 mammals, and 7 birds have been found in gopher tortoise burrows (Cox et al. 1994, Jackson and Milstrey 1989, Brandt et al. 1993, Kent and Snell 1994, Diemer 1992). Some of the arthropods, such as the gopher cricket (Ceuthrophilus spp.) and scarab beetles (Aephodius spp., Copris spp., and Onthophagus spp.) are obligate commensals that occur nowhere except in gopher burrows (Deyrup and Franz 1994). Overall, gopher tortoise burrows provide a diversity of microhabitats that engenders a higher species richness (both plant and animal) for the high pine community. Gopher tortoises are listed as species of special concern by Florida and are declining throughout the state because of habitat loss and illegal harvesting for food.

The Florida scrub lizard (Sceloporus woodi) occurs only in central and southcentral peninsular Florida and along both coasts in South Florida where it is

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restricted to scrub and scrubby high pine communities. Scrub lizards occur in open, sandy habitats and are often seen running along the ground, in contrast to their many relatives in western North America which are decidedly arboreal. The Florida scrub lizard is extremely endangered where it occurs in coastal scrubs in South Florida, and is already extinct or nearly so in southwest Florida (DeMarco 1992). In Ocala NF, and where its habitat persists on the Lake Wales Ridge, the species is still common.

The Florida gopher frog (Rana capito aesopus) most typically occurs in scrub and high pine communities where it lives almost exclusively in gopher tortoise burrows. They venture out at night to feed on arthropods, spiders and other frogs, and can sometimes be seen perched at the burrow entrance on rainy or cloudy days. Following heavy rains in spring or summer, gopher frogs migrate up to a mile to spawn in isolated wetland ponds. When the tadpoles transform in 3-5 months, they must leave the water and find a tortoise burrow of their own. The gopher frog is listed as a species of special concern by Florida and is the only listed amphibian in the South Florida Ecosystem.

The Highlands tiger beetle (Cicindela highlandensis) was known only from two scrubs on the southern Lake Wales Ridge, both of which have been destroyed by development (Deyrup 1989). No doubt there are many more scrub invertebrates yet to be described, and many that will go extinct before they are described.

Plant Species of Concern

Federally listed species that depend upon or utilize the scrub community in South Florida include: four-petal pawpaw (Asimina tetramera), Florida bonamia (Bonamia grandiflora), fragrant prickly-apple (Cereus eriophorus var. fragrans), pygmy fringe-tree (Chionanthus pygmaeus), Florida golden aster (Chrysopsis floridana), Florida perforate cladonia (Cladonia perforata), pigeon wings (Clitoria fragrans), short-leaved rosemary (Conradina brevifolia), Avon Park harebells (Crotalaria avonensis), Garretts mint (Dicerandra christmanii), scrub mint (Dicerandra frutescens), Lakelas mint (Dicerandra immaculata), scrub buckwheat (Eriogonum longifolium var. gnaphalifolium), snakeroot (Eryngium cuneifolium), Highlands scrub hypericum (Hypericum cumulicola), scrub blazing star (Liatris ohlingerae), scrub lupine (Lupinus aridorum), Brittons beargrass (Nolina brittoniana), papery whitlow-wort (Paronychia chartacea), Lewtons polygala (Polygala lewtonii), tiny polygala (Polygala smallii), wireweed (Polygonella basiramia), sandlace (Polygonella myriophylla), scrub plum (Prunus geniculata), Carters mustard (Warea carteri), and Florida ziziphus (Ziziphus celata). Biological accounts and recovery tasks for these species are included in The Species section of this recovery plan. The State listed pine pinweed (Lechea divaricata) also occurs in the scrub community (Appendix C).

The Florida ziziphus is a spiny shrub that occurs on the fringe of turkey oak (Quercus laevis) sandhills or yellow sand oak-hickory scrub communities, and is endemic to the Lake Wales Ridge. The Florida ziziphus prefers excessively

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